R1-2509145
discussion
Channel coding for 6GR interface
From MediaTek
Summary
MediaTek presents 10 observations and numerous proposals for 6G channel coding enhancements, covering QC-LDPC data channel improvements targeting 2-4x peak data rate gain over 5G and Polar code enhancements for control channels addressing payload size scalability, early termination, RNTI false alarm reduction, and high-order QAM support.
Position
MediaTek proposes studying 6G QC-LDPC designs capable of achieving 2-4x peak data rate over 5G, emphasizing that simply scaling existing 5G LDPC via additional parallel decoders is area-inefficient and undesirable. They introduce decoding cycle metrics (I_total = I_iter × I_cycle) to evaluate throughput-latency tradeoffs, identifying MCS=20 as the peak data rate bottleneck for BG1. For Polar code enhancements, they propose a new data integrity check mechanism to improve payload size scalability beyond the current 140-bit limit and early termination rate, noting that 5G distributed CRC design provides limited early termination benefit with >50% information bits processed before decoding termination. MediaTek requires studying new RNTI scrambling mechanisms to reduce RNTI-FA rate, presenting a specific proposal to shift CRC bits scrambled by RNTI to the payload beginning, and provides detailed simulation showing 5G design encounters >90% FA rate for certain payload sizes. They propose studying high-order QAM polar codes for both UCI performance enhancement and DCI spectral efficiency, presenting multi-level coding (MLC) with joint shaping results showing >0.5dB gain over 5G BICM. They support pair-wise orthogonality structures and BG size adaptation for different code rates as specific design directions.
Key proposals
- Proposal 1 (Sec 6G data channel coding enhancement): Study 6G QC-LDPC design to achieve 2x-4x peak data rate of 5G with acceptable performance-complexity tradeoff for both NW side and UE side provided that additional performance and complexity trade-offs required from 2 to 4 times peak data rate increase is minimized
- Proposal 2 (Sec Evaluation methodology / Iteration and decoding cycle per iteration evaluation): Consider I_total = I_iter × I_cycle as the estimation of total decoding cycles per CB, where I_cycle can be approximated by e/M, with e being the number of edges in a BG and M the number of edges available to be processed simultaneously
- Proposal 3 (Sec Evaluation methodology / Peak data rate evaluation): To ensure BLER performance is acceptable for all MCS, consider metric R_peak = min_X (R_X) to facilitate peak data rate evaluation for a decoder operating at maximum frequency, where I_min is the minimum iterations to satisfy BLER performance requirement
- Proposal 4 (Sec Enhancement directions): Study reduced number of iterations, reduced BG edges, parallelism structure, maximum lifting size>384, BG size adaptation for different code rates, and combination of above aspects to improve 2-4x peak data rate from 5G
- Proposal 5 (Sec Outer code design enhancements / Scalable data integrity check design): Study a new data integrity check mechanism with the aim to improve payload size scalability and early termination rate over 5G distributed CRC design
- Proposal 6 (Sec Outer code design enhancements / Scalable data integrity check design): Consider early termination rate metric E[d_stop]/K with methodology assuming SCL list size=8 and pure AWGN noise transmission
- Proposal 7 (Sec Outer code design enhancements / RNTI-FA reduction design): Study new mechanism of RNTI scrambling to reduce RNTI-FA rate
- Proposal 8 (Sec Outer code design enhancements / RNTI-FA reduction design): Consider methodology to facilitate DCI RNTI false alarm evaluation with Alt1 (evaluating max over RNTI patterns) and Alt2 (evaluating probability with distinct uniformly generated RNTIs for neighbor UEs)
- Proposal 9 (Sec Polar+high order QAM): Study high order QAM polar code for UCI performance enhancement and DCI SE enhancement
- Proposal 10 (Sec Evaluation methodology): Target BLER of 0.01 and target SNR = Reference SNR + [<0.5]dB, where Reference SNR is the SNR where BG1 achieves target BLER under Layer BP with 20 iterations
- Proposal 11 (Sec 6G data channel coding enhancement): Dual diagonal structure and Raptor code structures introduced in 5G QC-LDPC code can be leveraged in 6G QC-LDPC code design to achieve encoding latency reduction